Rotor Sheet Relief Openings for Stress Redistribution

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Solution Overview

Problem

Permanently excited electrical machines face mechanical stress limitations due to centrifugal forces and interference fits, restricting operational speed and requiring stronger, more complex rotor designs to avoid mechanical failure.

Innovation Solution

Incorporating a non-circular relief through-opening in the rotor sheet, inscribed within an incircle-free trapezoid, which is tilted to increase angular spacings beyond magnet pocket spacings, redistributes mechanical stress to structurally stronger regions, enhancing mechanical robustness and allowing higher operational speeds or reduced manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the rotor sheet is designed to withstand high mechanical stress from centrifugal forces and interference fits, then the electrical machine can operate at higher rotational speeds, but the rotor design becomes stronger and more complex

Engineering Contradiction:

Improverotational speedVSAvoid rotor design complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The rotor sheet is segmented into multiple sectors, with each sector containing magnet pockets and relief through-openings. This segmentation allows stress to be distributed across multiple independent regions rather than concentrated in a single structure, enabling the rotor to withstand higher rotational speeds without requiring an overly complex overall design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Relief through-openings are strategically positioned in specific regions of the rotor sheet where stress concentration occurs. These local modifications create areas of reduced stress concentration without compromising the overall structural integrity, allowing the rotor to operate at higher speeds while maintaining a relatively simple global design

Inventive Principle:

Principle #3Local quality

2Speed

Engineering Contradiction:

Improverotational speedVSAvoidmechanical strength

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

Material is extracted from specific regions of the rotor sheet to create relief through-openings. By removing material from high-stress concentration areas, the design reduces the mechanical strength requirements of those specific regions while maintaining overall rotor integrity, enabling operation at higher rotational speeds without requiring excessive overall strength

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The relief through-openings create local variations in the rotor sheet structure, providing stress relief in specific high-stress regions while maintaining adequate strength in other areas. This localized approach allows the rotor to operate at higher speeds without requiring a uniform increase in mechanical strength across the entire structure

Inventive Principle:

Principle #3Local quality

3Speed

If relief through-openings are added to reduce mechanical stress in weak regions, then the rotor can operate at higher speeds, but the manufacturing process becomes more complex

Engineering Contradiction:

Improverotational speedVSAvoidmanufacturing complexity

Core Design Contradiction:

SpeedVSEase of manufacture

Solution Approach 1:

The relief through-openings are designed and positioned in advance during the rotor sheet manufacturing process. By pre-planning the location and configuration of these stress-relief features, the manufacturing process can incorporate them efficiently without requiring complex post-processing or assembly operations, minimizing the increase in manufacturing complexity while achieving the goal of higher operational speeds

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design reduces mechanical stress in weak regions, enabling higher operational speeds or lower mechanical strength configurations while simplifying manufacturing, and provides a larger tolerance range for interference fits, thus improving the mechanical robustness and performance of electrical machines.

Implementation Method 1

redistributes mechanical stress to structurally stronger regions

Methodology Applied

Scientific EffectStress redistribution:

Data Source

PatentUS11190068B2Rotor sheet, rotor, and electrical machine, and method for producing a rotor

Publication Date: 2021.11.30 VALEO EAUTOMOTIVE GERMANY GMBH

AI summary

A rotor sheet includes a central cut-out and is divided into a plurality of sectors, each including a first half sector and a second half sector delimited from the first half sector by a radial central line, wherein a through-opening configuration, which has two parallel edge lines extending along an extension direction, is formed inside the first half sector, and a further through-opening configuration, mirror-symmetrical to the through-opening configuration with respect to the central line, is formed inside the second half sector, wherein the first through-opening configuration includes a relief through-opening inscribed inside an incircle-free trapezoid having two bases extending parallel to the central line and two legs extending on a first straight line having a first angular spacing from the central line, and on a second straight line having a second angular spacing from the central line, wherein the first and second straight lines intersect at an acute angle.